Nucleation

Abstract

Based on Turnbull's concept of the importance of transient nucleation during phase transformations in solids, a general theory of nucleation has been developed. The nucleation mechanism for reactions where stable nuclei appear only during cooling or plastic deformation has been clarified. The general theory makes possible quantitative description of the rates of nucleation of all phase transformations as well as of fracture cracks, slip bands, and magnetic transformations in solids.

Diffusion in the intermetallic compound NiAl

“…An atom is said to diffuse by an interstitial mechanism when it passes from one such site to one of its nearest-neighbour sites without permanently displacing any of the matrix atoms. The mechanism is known to operate in the diffusion of carbon and nitrogen in iron (Birchenall & Mehl 1947;Fisher et al 1948). It is not likely to be important in highly-ordered compounds like NiAl, nor are the 'interstitialcy' or 'Crowdien' mechanisms (Paneth 1950), which are both modified interstitial mechanisms.…”

Modeling and simulation of fragmentation of suddenly heated liquid metal jets.

“…Cavitation theory for the vapor bubbles that rise and collapse in an overheated liquid state has been well investigated in the past. But the formation of cavities under strong negative pressure displays features that are different from those suggested by the theory of void nucleation in the superheated state [6][7].…”

“…The theory of nucleation [6][7][10][11][12] predicts that the rate of critical cavity formation is given by…”

“…However, the problem of which mechanism is mainly responsible for liquid fragmentation and the production of liquid droplets was not properly studied. Nevertheless, various mechanisms that lead to liquid fragmentation do exist and were investigated in the 1940s and 1970s by several authors [6][7][8][9][10][11][12].…”

Kinetics of oriented crystallization of polymers in the linear stress-orientation range in the series expansion approach

“…The half-time analysis has been used by Spruiell and coworkers [4,5] to discuss problems which appear in applying the experimental kinetics data in modeling of real melt spinning processes. Other mechanisms possible under variable molecular orientation and temperature, such as athermal nucleation [48][49][50] and memory effects [51][52][53][54] which result from transient distribution of cluster sizes [50,55] and transient molecular orientation [56,57] have been indicated by Ziabicki and coworkers [46,49,55,[58][59][60] and Jarecki [61] basing on the AvramiEvans approach. At large undercoolings, the nucleation mechanism may no longer be valid and a low temperature limit has been indicated for nucleation-controlled crystallization [55].…”